Our ultimate goal is to identify genes which are active in promoting metastatic behavior of tumor cells. We propose to use two recently developed phenotypic selection ethods to identify cDNAs which are expressed in metastatic tumor cells and which may be involved in particular aspects of the metastatic process. We will apply our recently developed assay for the positive selection of slowly growing cells, coupled with classical gene transfer and differential expression methodology, to identify growth suppressor genes which are differentially expressed in metastatic versus non-metastatic melanoma cells. In addition will attempt to adapt a method for selecting cell variants which are capable of invasion as election method for genes which are involved in the invasion process. The advantage to is approach is that interesting genes are initially selected on the basis of a desired phenotype, not merely differential expression. 1. Determine the effect of our previously isolated growth inhibitory plasmids on the growth characteristics and metastatic behavior of established high and low metastatic potential melanoma lines. 2. Identify genes which are expressed in metastatic tumor cells and non-metastatic tumor cells which are capable of inhibiting cell proliferation. 3. Develop a phenotypic selection protocol for the isolation of invasion promoting genes. 4. Assess the patterns of expression of putative growth inhibitory or invasion promoting genes to determine whether they are differentially expressed in metastatic cells versus non-metastatic cells. 5. Determine if the expression of any putative growth inhibitory or invasion promoting genes modulates components of the extracellular matrix and matrix receptors which have been previously correlated with the metastatic phenotype.